Choice of modality
- CT of the head in stroke is generally the first investigation because of high availability. It detects about 60% of infarcts in the first 3 to 6 hours, and almost always thereafter.
- MRI of the head in stroke is generally less available, but preferred if there are no MRI contraindications, and your clinic has established procedures for its performance in acute stroke (if you do not know, it is reasonable to assume that there is not, and do CT).
Still not sure? See: CT vs MRI in stroke
According to UK guidelines, imaging should be performed immediately for people with suspected acute stroke if any of the following apply:
- Indications for thrombolysis or early anticoagulation treatment
- Current anticoagulant treatment
- Any known bleeding tendency
- Depressed level of consciousness of Glasgow coma scale (GCS) of less than 13
- Unexplained progressive or fluctuating symptoms
- Papilledema, neck stiffness or fever
- Severe headache at onset of stroke symptoms.
"Immediately" is defined as 'ideally the next slot and definitely within 1 hour.
In case of acute stroke without indications for immediate imaging, it should be performed within a maximum of 24 hours after onset of symptoms.
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